From the latest available statistics of Irish births and of abortions in Britain, it seems clear that last year more than half of all first pregnancies here were outside of marriage - an astonishingly high figure for a State where 25 years ago this proportion was less than one-fifth.
Since the mid-1960s, the number of non-marital births has been rising steadily, from under 1,000 in 1965 to more than 15,000 last year. The number of abortions carried out in Britain on women with addresses in the Republic has also been rising, although since 1981 at a much slower rate than non-marital births: between 1981 and 1998 the number of non-marital births increased almost four-fold, whereas the number of Irish abortions in Britain rose by two-thirds.
These abortion figures may underestimate the number of Irish abortions abroad, both because some Irish women having abortions in Britain may give a British rather than an Irish address and because a certain number may go to a continental country, such as Denmark. Making allowance for the fairly small proportion of abortions - perhaps 15 to 20 per cent - being carried out on married women, and leaving aside the under-estimation factor mentioned, the proportion of non-marital pregnancies aborted in Britain seems to have fallen since 1981 from around half to one-quarter.
This greatly reduced proportion of such pregnancies aborted probably reflects more tolerant societal attitudes towards non-marital pregnancies during the past two decades and the consequent reduction in social pressures. Such pressures were undoubtedly one of the factors that led to the very high abortion rates of non-marital pregnancies in the 1970s.
Last year 28 per cent of all births were non-marital, which means that, when abortions are taken into account, at least one-third of all pregnancies are non-marital, but, as mentioned, the non-marital proportion of first pregnancies is much higher.
There do not seem to be figures on the proportion of abortions that involve first pregnancies, but even if these constitute only half of the total - and the proportion of first pregnancy abortions is certainly higher than that - over half of all Irish pregnancies are now non-marital.
Clearly this reflects a drift away from marriage - either by way of postponement or abandonment. Both factors are clearly at work - but at this stage it is impossible to say in what proportions.
The scale of the postponement factor may, however, be judged from the fact that between 1984 and 1995 the proportion of marriages involving women under 25 dropped by two-thirds - while the number of marriages of women aged 26-35 rose by a similar proportion.
This postponement factor finds a reflection in the sharp rise in the age at which married women are having children. Between 1984 and 1998 the proportion of marital births to women aged 23-26 fell from 23 per cent to 15 per cent, while the proportion to mothers aged 31-35 jumped from 26 per cent to 37 per cent.
Within the past three years, this phenomenon has gathered further momentum. Despite the fact that the number of marital births to women aged 27 and under fell by a further 22 per cent during this brief period, the overall decline in the number of marital births was first halted in 1996, and then reversed in 1997.
This remarkable development has been exclusively accounted for by an increase of 20 per cent in first marital births to women aged 30-34 and of almost 30 per cent in first marital births to women aged 35-39. This is clearly a "biological clock" phenomenon, but one that is disturbing because of the extent to which it involves so many late first pregnancies.
The demographic changes that have been taking place involve more than just postponement of marriage and of first marital pregnancies. In the past, non-marital births largely involved teenagers and women in their early 20s: as late as 1981 over four-fifths of non-marital births were to women under 25.
However, in the 14 years since 1984 the proportion of such births to women over 25 has jumped from 18 to 43 per cent. More than a quarter of children born to women aged 25-29 last year were born to single women, as were one in seven children born to women in their 30s.
It is also significant in this connection that, whereas in 1984 only 38 per cent of non-marital children born to women over 24 were second or later children, last year this percentage rose to 58 per cent.
These data provide clear evidence of the fact that a significant proportion of couples effectively reject the idea of marriage, even after they have reached the stage of starting a family.
These fundamental social changes, the scale of which do not seem to have impinged fully on public awareness, raise difficult questions for those engaged in formulating public policy. Our social structures, and indeed the Constitution, remain firmly based on the concept of marriage as the sole basis of the family, yet non-marital families are now a significant, and growing, element of our social structure.
Should we give constitutional and legal recognition to this new factor - as we have already started to do in relation to some social welfare provisions?
Most people engaged in social policy favour such a course, most especially those who are working on the ground, dealing with these problems. There is much to be said for this view: for when laws fail to take account of the reality of the society to which they apply, they quickly lose credibility.
That was eminently true, for example, of the ban on divorce, which may have been a stabilising factor in our society during the first half-century of the existence of our State, but had, I believe, outlived its usefulness by the end of the 1970s.
What does not seem to have been addressed, however, is the question of whether such adjustments to our constitutional and legal provisions could usefully be accompanied by any offsetting measures designed to diminish the adverse social effects of some current trends, for there are adverse social effects.
Thus the loss of the additional stability offered by marriage, and by the rights of spouses and children within marriage - not all of which can reasonably be replicated in the case of non-marital unions - is a negative social factor with which the public authorities can legitimately concern themselves. Moreover the rapid shift to late marriages and late family initiation is undesirable in terms of the health of both the mother and the children.
If there were ways in which the public authorities could counteract this trend, it would, in my view, be entirely legitimate and appropriate for them to do so.
I am aware of the strong view of sociologists that social policy should not be judgmental, and where in the past it has been so, the results have sometimes been negative, e.g. in relation to non-marital births. However, at this stage in the evolution of our family structures, some of these considerations carry less force, and non-judgmentalism can become an excuse for failing to address serious social issues.
It may well be that for practical reasons it would be difficult to devise social measures that would help to promote marriage in preference to non-marital unions and reverse the trend towards late marriages and late first pregnancies - although paid maternity and paternity leave of the kind that exists in some continental countries, would help to bring forward the initiation of families.
We should at least be prepared to discuss these issues on their merits rather than being intimidated by a laissez-faire liberalism into ignoring them. In the interests of the greater health and happiness of future generations, some space should be found for a rational debate on these matters which would avoid the futile polarisation between fundamentalism and extreme forms of liberalism that in the past marred discussion of important social issues.